Lets look at this from the point of view of the driver of a car. Your vehicle has particular dimensions. You are driving in a lane which has particular dimensions and on a road which has particular dimensions. There is a bicycle ahead of you. Consider three cases:

1. There is plenty of room to overtake
2. There is barely enough room to overtake
3. There is no room to overtake

In cases one and two the result is clear. You either overtake safely or not at all. In case two many different things can happen, and one or the largest variables is the behaviour of the driver of the overtaking vehicle.

Some drivers are very cautious. Others less so. Most of the risk is born by the bicycle rider and for some drivers this means that there is no risk at all. From the perspective of the bicycle rider the safest approach is to assume that the driver of the car will take the risk and overtake in this situation.

As a bicycle rider you should never case two. Never allow barely enough room to overtake. Always position yourself on the road by looking at the line to your right which delineates the lane you are driving in. Ride a consistent line and consider how much overtaking space exists in the lane. Keep an eye out for situations where cars might barely overtake. If this can happen, move to the right to turn case two into case three.